The present invention relates to a structure for supporting a diaphragm spring employed in a friction clutch for an automobile and others.
A conventional friction clutch basically has a structure as shown in FIG. 1. In FIG. 1, a frictional facing 3 is positioned between a flywheel 1 of an engine and an annular pressure plate 2. The facing 3 is fixed to an outer peripheral portion of a clutch disc 5 connected to an output shaft 4 (only a center line thereof is illustrated). When the pressure plate 2 presses the facing 3 onto the flywheel 1, the clutch engages and a torque is transmitted from a flywheel 1 through the disc 5 to the output shaft 4. A diaphragm spring 6 for forcing the pressure plate 2 toward the facing 3 is disposed at the rear of the pressure plate 2 opposite to the disc 5. The outer peripheral portion of the spring 6 is seated on a projection 7 on the rear surface of the pressure plate 2. When the inner peripheral portion of the spring 6 is pushed by a release bearing 8 toward the disc 5, the spring 6 elastically deforms into a shape shown by a phantom line 6a and releases the force against the pressure plate 2, so that the clutch disengages. The outer periphery and the rear surface of the spring 6 are covered by a clutch cover 10. The clutch cover 10 includes a substantially annular end wall 11 and a cylindrical peripheral wall 12 which inclines and projects from the outer periphery of the end wall 11 toward the flywheel 1 and is fixed at the end thereof to the flywheel 1.
The end wall 11 is provided at the inner periphery with circumferentially spaced integral projections or tabs 13. The tabs 13 are bent and projected from the end wall 11 toward the pressure plate 2 through recesses 15 of the spring 6, respectively. Free ends 14 of the tabs 13 are positioned between the pressure plate 2 and the spring 6. A pair of wire rings 19 and 20 are disposed at the outside, in the radial direction of the spring 6, of the tabs 13. The wire rings 19 and 20 form fulcrums for the spring 6. The projections or tabs 13 support the radially inner peripheries and the sides opposite to the spring 6 of the wire rings 19 and 20. The wire ring 19 is disposed between the spring 6 and the wall 11, and the wire ring 20 is disposed between the spring 6 and the ends 14 of the tabs 6.
As shown in FIG. 2, the spring 6 is provided with slits 16 which extend radially from the inner periphery to the radially middle or outer portion of the spring 6. The recesses 15 are formed by the radially outer ends of the slits 16 which are recessed and widened in the circumferential direction of the spring 6.
In the conventional clutch described above, it is impossible to avoid the rotation of the spring 6 relative to the clutch cover 10 which is caused by various vibration source including the engine, and thus, the tabs 13 collide against the edges of the recesses 15. And, in the conventional structure, the tabs 13 collide, in the linear contact condition, against round corners 23 between inner peripheral edges 21 extending in the circumferential direction of the spring 6 and inner side edges 22 extending substantially in the radial direction of the spring 6. The linear contact condition described above generates a very strong pressure between the tabs 6 and the round corners 23, so that the collided portions may be remarkably abraded and bite into each other, which reduces stability of the operation characteristic of the clutch and prevents smooth and light operation of the clutch. Further, in the known structure, the tabs 13 may deform and the wire rings 19 and 20 may deviate radially from the correct positions, which also may reduce the stability of the characteristic of the clutch.
Accordingly, it is an object of the invention to provide an improved structure, overcoming the above-noted problems, in which structures of projections or tabs of a clutch cover for supporting wire rings are improved.
According to the invention, a structure for supporting a diaphragm spring in a clutch comprises a diaphragm adapted to force a pressure plate provided with slits radially extending from the inner periphery of the spring; tabs extending from a clutch cover through radially outer portions of the slits; and a pair of wire rings employed as fulcrums for said spring and supported by said tabs; and is characterized in that; said tabs are provided with straight portions extending substantially perpendicular to the spring and engaging with the inner peripheries of the recesses, respectively, and each straight portion is provided at the side with protrusions protruding toward a portion of the inner side edge of the recess distant from the corner between the inner side edge and the inner periphery of the recess.
Other and further object, features and advantages of the invention will appear more fully from the following description of the preferred embodiments of the invention.